Dilator

ABSTRACT

The shaft of a dilator has a tapered part whose outer diameter at a distal end is smaller than at a proximal end, and either a distal end part and a proximal end part, or a proximal end part without a distal end part. If only the proximal end part is provided, the pitch of neighboring sections of a spirally-arranged protruding portion on the tapered part is larger than that on the proximal end part. If both the proximal end part and the distal end part are provided, the pitch of neighboring sections of the spirally-arranged protruding portion on the tapered part is larger than those on the distal end part or the proximal end part.

This application is a continuation application of InternationalApplication No. PCT/JP2018/035089, filed Sep. 21, 2018, which claimspriority to International Application PCT/JP2018/011673, filed Mar. 23,2018. The contents of these applications are incorporated herein byreference in their entirety.

BACKGROUND

The disclosed embodiments relate to a dilator.

Dilators that enable treatment by enlarging a penetration-hole formed inthe wall of a patient's digestive tract or the like are known. Thedistal end of the dilator is inserted into the penetration-hole formedin the wall, and the penetration-hole is expanded by pushing a taperedpart into the penetration-hole. Such a dilator is disclosed according toJapanese Patent Document JP2008-11867.

SUMMARY

In the dilator mentioned above, a sufficient thrust could not beachieved with respect to the tapered part, which experiences anincreased resistance when being pushed into a penetration-hole orconstricted part, and in some cases the penetration-hole or constrictedpart could not be sufficiently expanded.

The present disclosure has an object of providing a dilator that caneasily widen the diameter of a penetration-hole formed in the wall of adigestive tract or the like, and can suppress damage to the wall of thedigestive tract or the like.

In order to achieve the object, a dilator according to an aspect of thepresent disclosure comprises a shaft in a hollow shape, and a grip partthat is provided on a proximal end of the shaft. The shaft comprises atapered part in which an outer diameter of a distal end is smaller thanan outer diameter of a proximal end; and either (i) a distal end partthat is provided on a distal end side of the tapered part and whichextends toward the distal end side and a proximal end part that isprovided on a proximal end side of the tapered part and which extendstoward the proximal end side, or (ii) the proximal end part that isprovided on the proximal end side of the tapered part and which extendstoward the proximal end side, without the distal end part. Aspirally-arranged protruding portion is provided on an outer peripheralface of the shaft, and the spirally-arranged protruding portion has gapsbetween sections that are neighboring along an axis of the shaft. If theshaft does not include the distal end part, a pitch of sections of thespirally-arranged protruding portion provided on the tapered part, whichare neighboring along the axis, is larger than the pitch of sections ofthe spirally-arranged protruding portion provided on the proximal endpart, which are neighboring along the axis. If the shaft includes thedistal end part, a pitch of sections of the spirally-arranged protrudingportion provided on the tapered part, which are neighboring along theaxis, is larger than the pitch of sections of the spirally-arrangedprotruding portion provided on the distal end part or the proximal endpart, which are neighboring, respectively, along the axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall view of a dilator of the disclosed embodiments;

FIG. 2 is a diagram showing a distal end side section of a dilator ofthe disclosed embodiments;

FIG. 3 is a diagram showing an overall view of a dilator of thedisclosed embodiments;

FIG. 4 is a partial cross-sectional view of a distal end side section ofa dilator of the disclosed embodiments;

FIG. 5 is an overall view of a dilator of the disclosed embodiments;

FIG. 6 is a partial cross-sectional view of a distal end side section ofa dilator of the disclosed embodiments;

FIG. 7 is a partial cross-sectional view of a distal end side section ofa dilator of the disclosed embodiments;

FIG. 8 is a partial cross-sectional view of a distal end side section ofa dilator of the disclosed embodiments;

FIG. 9 is a partial cross-sectional view of a distal end side section ofa dilator of the disclosed embodiments;

FIG. 10 is a partial cross-sectional view of a distal end side sectionof a dilator of the disclosed embodiments;

FIG. 11 is a partial cross-sectional view of a distal end side sectionof a dilator of the disclosed embodiments;

FIG. 12 is a schematic view of a distal end side section of the dilatorof the disclosed embodiments;

FIG. 13 is a schematic view showing a distal end side section of adilator of the disclosed embodiments;

FIG. 14 is a schematic view showing a distal end side section of adilator of the disclosed embodiments;

FIG. 15 is a schematic view showing a distal end side section of adilator of the disclosed embodiments;

FIG. 16 is a schematic view showing a distal end side section of adilator of the disclosed embodiments; and

FIG. 17 is a diagram showing a distal end side section of a dilator ofthe disclosed embodiments.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings. Note that the dimensions of the dilatorsshown in the drawings are dimensions shown for the purpose offacilitating an understanding of the technical matters, and do notcorrespond to the actual dimensions.

A dilator of the present disclosure will be described with reference tothe drawings. FIG. 1 is an overall view of a dilator 1 of the disclosedembodiments. Furthermore, in FIG. 1, the left side of the drawing is thedistal end side (far side) inserted into the body, and the right side isthe proximal end side (near side) operated by an operator such as aphysician.

In FIG. 1, the dilator 1 includes a multilayered body 7 including afirst coil 3 formed by winding a plurality of metal wires into a hollowshape, and a second coil 5 formed by winding a single metal wire onto anouter peripheral face 3A of the first coil 3 in an opposite direction(wound clockwise toward the distal end) to the first coil 3 (woundcounterclockwise toward the distal end); and a hollow connector 9connected to a proximal end of the multilayered body 7.

The wires constituting the first coil 3 and the second coil 5 are, forexample, metal wires made of stainless steel or a superelastic alloysuch as nickel-titanium, or are resin wires.

The first coil 3 is formed, for example, by winding ten metallic wiresmade of stainless steel. The first coil 3 has a hollow shape and isformed having a lumen 3B that passes through from the distal end to theproximal end. The first coil 3 includes a proximal end part 3C, atapered part 3D, and a distal end part 3E. The first coil 3 correspondsto a shaft.

The proximal end part 3C is positioned on the proximal end side of thedilator 1, and a connector 9 is connected to the proximal end thereof.Furthermore, the proximal end part 3C has a substantially constant outerdiameter from the proximal end to the distal end.

The tapered part 3D is positioned on the distal end side of the proximalend part 3C, extends from the distal end of the proximal end part 3Ctoward the distal end side, and has an outer diameter that decreasestoward the distal end side.

The distal end part 3E is located on the distal end side of the taperedpart 3D and extends from the distal end of the tapered part 3D towardthe distal end side. The distal end part 3E has a substantially constantouter diameter from the proximal end to the distal end. As a result, thefirst coil 3, which serves as the shaft, has a hollow shape in which theouter diameter of the distal end is smaller than the outer diameter ofthe proximal end.

The second coil 5 is, for example, a single metal wire which is woundaround onto the outer peripheral face 3A of the first coil 3 in anopposite direction (wound clockwise toward the distal end) to the firstcoil 3 (wound counterclockwise toward the distal end). Here, the metalwire is closely wound (without spacing) on the proximal end side, and iswound with spacing on the distal end side of the proximal end part 3C,the tapered part 3D, and the distal end part 3E. A spirally-arrangedprotruding portion that protrudes toward the exterior (radially outwardfrom the outermost surface and outermost part of the dilator 1) isprovided on the outer peripheral face 3A of the first coil 3 as a resultof the section of the second coil 5 being wound with spacing. That is,the section of the second coil 5 wound with spacing forms aspirally-arranged protruding portion on the outer peripheral face 3A ofthe first coil 3. The spirally-arranged protruding portion has gapsbetween sections that are neighboring (gaps between adjacent windings ofthe metal wire) along the axis A (longitudinal axis) of the first coil3. The dilator 1 can also be moved forward by a rotation operation ofthe dilator 1 as a result of a screw action of the spirally-arrangedprotruding portion.

Furthermore, the pitch of sections provided on the tapered part 3D, saidsections being neighboring along the axis A of the second coil 5, isconfigured to be larger than the pitch of sections provided on theproximal end part 3C and the distal end part 3E, said sections beingneighboring along the axis A of the second coil 5. That is to say, interms of the sections being neighboring along the axis A of the secondcoil 5, the pitch L1 on the distal end side of the proximal end part 3C,the pitch L2 on the tapered part 3D, and the pitch L3 on the distal endpart 3E are configured such that L1, L3<L2 (all the pitches L1 and allthe pitches L3 are smaller than any of the pitches L2). Note that thepitches on the distal end side of the proximal end part 3C may be equalor different. The pitches on the tapered part 3D may be equal ordifferent.

Furthermore, the metal wire of the second coil 5 is wound such that theamount of separation between neighboring metal wires gradually decreasestoward the proximal end side of the proximal end part 3C. As a result ofthis configuration, the rigidity of the dilator 1 (multilayered body 7)in the axial direction can be gradually changed, and the dilator 1 caneasily advance along a path even when a curved path is to be travelled.

The length of the dilator in the present embodiment and in the otherembodiments described below is, for example, 2000 mm, and may be 1600 mmto 2500 mm; the length of the distal end part 3E is, for example, 10 mm,and may be 0 to 100 mm; and further, the length of the tapered part 3Dis, for example, 30 mm, and may be 5 to 100 mm. The inner diameter atthe distal end of the first coil 3 is, for example, 0.7 mm, and may be0.4 to 1.0 mm; and the inner diameter at the proximal end of the firstcoil 3 is, for example, 1.5 mm, and may be 1.0 to 3.0 mm. The outerdiameter at the distal end of the second coil 5 is, for example, 1.84mm, and may be 0.8 to 3.0 mm; and the outer diameter at the proximal endof the second coil 5 is, for example, 2.64 mm, and may be 1.4 to 5.0 mm.Furthermore, the diameter of the metal wires of the first coil 3 is, forexample, 0.21 mm, and may be 0.1 to 0.5 mm; and the diameter of themetal wires of the second coil 5 is, for example, 0.36 mm, and may be0.1 to 0.5 mm.

The pitches L1 and L3 of the second coil 5 on the proximal end part 3Cand the distal end part 3E are, for example, 1.5 mm, the pitch L2 of thesecond coil 5 on the tapered part 3D is, for example, 2 mm, and theratio between the two ((L1 or L3)/L2) is 0.75. The pitches L1 and L3 ofthe second coil 5 on the proximal end part 3C and the distal end part 3Emay be 0.2 to 4 mm, the pitch L2 of the second coil 5 on the taperedpart 3D may be 0.25 to 5 mm, and the ratio between the two is in a rangeof 0.04 to 1.

The connector 9, which is a grip part, is a part that an operator usesto push the dilator into the body or perform a rotation operation. Thedistal end of the connector 9 is connected to the proximal end of thefirst coil 3 and the proximal end of the second coil 5. The connector 9is made of resin, and has a hollow shape having a lumen whichcommunicates with the lumen 3B of the first coil 3.

In the dilator 1 of the present disclosure, a spirally-arrangedprotruding portion (second coil 5) that protrudes toward the exterior isprovided on the outer peripheral face 3A of first coil 3, which servesas the shaft, and the spirally-arranged protruding portion has gapsbetween sections along the axial direction of the first coil 3. Thisconfiguration not only enables the dilator to be moved forward in aconventional fashion by a pressing operation, but also to be movedforward by a rotation operation as a result of the spirally-arrangedprotruding portion.

Furthermore, the pitch of sections provided on the tapered part 3D, saidsections being neighboring along the axis A of the second coil 5, isconfigured to be larger than the pitch of sections provided on theproximal end part 3C and the distal end part 3E, said sections beingneighboring along the axis A of the second coil 5. As a result, when thedilator 1 is rotated, the tapered part 3D of the first coil 3 has asmaller frictional resistance with the target object (for example, adigestive tract such as the stomach, or the liver) than the proximal endpart 3C and the distal end part 3E. As a result, the diameter of apenetration-hole formed in the wall of a digestive tract or the like canbe easily widened, and it is possible to suppress damage to the targetobject which can occur due to intrusion into the target object.

Moreover, because the shaft is constituted by the first coil 3, in whicha plurality of metal wires is wound in a hollow shape, the flexibilityof the shaft, and the torquability by the first coil 3 can be improved.Furthermore, because the spirally-arranged protruding portion iscomposed of the second coil 5, in which a single metal wire is woundaround onto the outer peripheral face 3A of the first coil 3, thespirally-arranged protruding portion can be easily formed, and theelasticity of the second coil 5 enables the flexibility of distal end ofthe dilator 1 to be ensured, and the torquability to be improved.Moreover, because the wires of the first coil 3 and the second coil 5are wound in mutually opposite directions, even when the dilator 1 isrotated in a direction that opens the first coil 3, a force is appliedin a direction that closes the second coil 5, which inhibits the firstcoil 3 from opening and enables the force applied to the connector 9 ofthe dilator 1 to be delivered to the distal end side.

Next, an example of a usage mode of the dilator will be described.

First, a target object is punctured with an introducer needle to form apenetration-hole. Then, after inserting a guide wire into a lumen of theintroducer needle, the introducer needle is removed.

Next, the proximal end of the guide wire is inserted into the lumen ofthe dilator, and the dilator is inserted. Then, the dilator is pushedforward while rotating the shaft to expand the hole of the puncturedpart. At this time, the tapered portion advances due to a screw actionor the like of the spirally-arranged protruding portion caused by arotation operation of the shaft, and the penetration-hole can besmoothly expanded by the tapered part.

FIG. 2 is a diagram showing a distal end side section of a dilator 10 ofthe disclosed embodiments.

Furthermore, in FIG. 2, the left side of the drawing is the distal endside (far side) inserted into the body, and the right side is theproximal end side (near side) operated by an operator such as aphysician.

The dilator 10 of the present embodiment has the same basic structure asthe dilator 1, and therefore, the same reference numerals are given tothe same members, and the description will not be repeated.

In FIG. 2, the dilator 10 includes a multilayered body 17 including afirst coil 3 formed by winding a plurality of metal wires into a hollowshape, and a second coil 5 formed by winding a single metal wire onto anouter peripheral face 3A of the first coil 3 in an opposite direction(wound clockwise toward the distal end) to the first coil 3 (woundcounterclockwise toward the distal end); and a hollow connector 9connected to a proximal end of the multilayered body 17. However, thedilator 10 differs from the dilator 1 in that a tip 6 is providedinstead of the distal end part 3E of the first coil 3 of the dilator 1.In the present embodiment, the first coil 3, which is provided with thetip 6 on the distal end, corresponds to the shaft.

The tip 6 is formed by pouring a brazing material (such as a silver-tinbrazing material or a gold-tin brazing material) into the distal end ofthe first coil 3, and the shape thereof is a substantially cylindricalhollow shape. Moreover, unlike the distal end of the multilayered body7, the surface of the tip 6 does not have an uneven shape, and is flat.

In the present embodiment, the pitch of sections provided on the taperedpart 3D, said sections being neighboring along the axis A of the secondcoil 5, is configured to be larger than the pitch of sections providedon the proximal end part 3C, said sections being neighboring along theaxis A of the second coil 5. That is to say, in terms of the sectionsbeing neighboring along the axis A of the second coil 5, the pitch L11on the distal end side of the proximal end part 3C and the pitch L12 onthe tapered part 3D are configured such that L11<L12.

According to the dilator 10 having such a configuration, the sameeffects as those of the dilator 1 can be obtained. That is to say, whenthe dilator 10 is rotated, the tapered part 3D of the first coil 3 has asmaller frictional resistance with the target object (for example, adigestive tract such as the stomach, or the liver) than the proximal endpart 3C. As a result, the diameter of a penetration-hole formed in thewall of a digestive tract or the like can be easily widened, and it ispossible to suppress damage to the target object which can occur due tointrusion into the target object. Furthermore, because the tip 6 havinga flat surface is connected to the distal end of the multilayered body17, the insertability into a punctured part is further improved by firstpushing the dilator with respect to the punctured part, and then pushingthe dilator while applying a rotation.

FIG. 3 is an overall view of a dilator 20 of the disclosed embodiments.Furthermore, in FIG. 3, the left side of the drawing is the distal endside (far side) inserted into the body, and the right side is theproximal end side (near side) operated by an operator such as aphysician.

In FIG. 3, the dilator 20 includes a shaft 21, a spirally-arrangedprotruding portion 22, and a connector 9 that is connected to theproximal end of the shaft 21.

The shaft 21 has a hollow shape and is formed having a lumen 21A thatpasses through from the distal end to the proximal end. Furthermore, theshaft 21 includes a proximal end part 23, a tapered part 24, and adistal end part 25.

The material forming the shaft 21 and the spirally-arranged protrudingportion 22 is not particularly limited as long as it ensures theflexibility of the tapered part 24 and the distal end part 25 and isbiocompatible, and examples include stainless steel, superelastic alloymaterials such as nickel-titanium alloy, and synthetic resins such aspolyvinyl chloride resins, urethane resins, polyolefin resins, polyamideresins, and fluorine resins.

The proximal end part 23 is positioned on the proximal end side of thedilator 20, and a connector 9 is connected to the proximal end thereof.Furthermore, the proximal end part 23 is provided on the proximal endside of the tapered part 24 and extends toward the proximal end side.The proximal end part 23 has a substantially constant outer diameterfrom the proximal end to the distal end.

The tapered part 24 is connected to the distal end of the proximal endpart 23, extends from the distal end of the proximal end part 23 towardthe distal end side, and has a shape which is tapered toward the distalend side.

The distal end part 25 is connected to the distal end of the taperedpart 24 and extends from the distal end of the tapered part 24 towardthe distal end side. The distal end part 25 has a substantially constantouter diameter from the proximal end to the distal end. As a result, theshaft 21 has a hollow shape in which the outer diameter of the distalend is smaller than the outer diameter of the proximal end.

A spirally-arranged protruding portion 22 is provided on the outerperipheral face 21B of the shaft 21 so as to protrude toward theexterior (from the outermost surface and outermost part of the dilator20). The spirally-arranged protruding portion 22 is provided on a distalend side section of the proximal end part 23, the tapered part 24, andthe distal end part 25, and has gaps between sections that areneighboring along an axis A of the shaft 21. That is to say, sections ofthe spirally-arranged protruding portion 22 that are neighboring aremutually separated. The spirally-arranged protruding portion 22 isintegrally formed with the shaft 21 by casting or the like.

The pitch of sections provided on the tapered part 24, said sectionsbeing neighboring along the axis A of the spirally-arranged protrudingportion 22, is configured to be larger than the pitch of sectionsprovided on the proximal end part 23 and the distal end part 25, saidsections being neighboring along the axis A of the spirally-arrangedprotruding portion 22. That is to say, in terms of the sections beingneighboring along the axis A of the spirally-arranged protruding portion22, the pitch L21 on the proximal end part 23, the pitch L22 on thetapered part 24, and the pitch L23 on the distal end part 25 areconfigured such that L21, L23<L22 (all the pitches L21 and all thepitches L23 are smaller than any of the pitches L22). Note that thepitches on the proximal end part 23 and the distal end part 25 may beequal or different. The pitches on the tapered part 24 may be equal ordifferent.

In the dilator 20 of the present embodiment, a spirally-arrangedprotruding portion 22 that protrudes toward the exterior is provided onthe outer peripheral face 21B of shaft 21, and the spirally-arrangedprotruding portion 22 has gaps between sections that are neighboringalong the axis A of the shaft 21. This configuration not only enablesthe dilator to be moved forward in a conventional fashion by a pressingoperation, but also to be moved forward by a rotation operation as aresult of the spirally-arranged protruding portion 22.

Furthermore, the pitch of sections provided on the tapered part 24, saidsections being neighboring along the axis A of the spirally-arrangedprotruding portion 22, is configured to be larger than the pitch ofsections provided on the proximal end part 23 and the distal end part25, said sections being neighboring along the axis A of thespirally-arranged protruding portion 22. As a result, when the dilator20 is rotated, the tapered part 24 of the shaft 21 has a smallerfrictional resistance with the target object (for example, a digestivetract such as the stomach, or the liver) than the proximal end part 23and the distal end part 25. As a result, the diameter of apenetration-hole formed in the wall of a digestive tract or the like canbe easily widened, and it is possible to suppress damage to the targetobject which can occur due to intrusion into the target object.

FIG. 4 is a partial cross-sectional view of a distal end side section ofa dilator 30 of the disclosed embodiments. Furthermore, in FIG. 4, theleft side of the drawing is the distal end side (far side) inserted intothe body, and the right side is the proximal end side (near side)operated by an operator such as a physician.

In FIG. 4, the dilator 30 includes a shaft 31, a spirally-arrangedprotruding portion 32, and a connector 9 that is connected to theproximal end of the shaft 31 (see FIG. 3). The materials forming theshaft 31 and the spirally-arranged protruding portion 32 are the same asthe materials forming the shaft 21 and the spirally-arranged protrudingportion 22 of the dilator 20.

The shaft 31 has a hollow shape and is formed having a lumen 31A thatpasses through from the distal end to the proximal end. Furthermore, theshaft 31 includes a proximal end part 33 and a tapered part 34. Thedilator 30 of the present embodiment differs from the dilator 20 in thatit does not have a distal end part.

The configurations of the proximal end part 33 and the tapered part 34are the same as those of the proximal end part 23 and the tapered part24. Furthermore, a spirally-arranged protruding portion 32 is providedon the outer peripheral face 31B of the shaft 31 so as to protrudetoward the exterior (from the outermost surface and outermost part ofthe dilator 30). The spirally-arranged protruding portion 32 is providedon a distal end side section of the proximal end part 33, and thetapered part 34, and has gaps between sections that are neighboringalong an axial direction of the shaft 31. That is to say, sections ofthe spirally-arranged protruding portion 32 that are neighboring aremutually separated. The spirally-arranged protruding portion 32 isintegrally formed with the shaft 31 by casting or the like.

The pitch of sections provided on the tapered part 34, said sectionsbeing neighboring along the axis A of the spirally-arranged protrudingportion 32, is configured to be larger than the pitch of sectionsprovided on the proximal end part 33, said sections being neighboringalong the axis A of the spirally-arranged protruding portion 32. That isto say, in terms of the sections being neighboring along the axis A ofthe spirally-arranged protruding portion 32, the pitch L31 on theproximal end part 33 and the pitch L32 on the tapered part 34 areconfigured such that L31<L32 (all the pitches L31 are smaller than anyof the pitches L32). Note that the pitches on the proximal end part 33may be equal or different. The pitches on the tapered part 34 may beequal or different.

In the dilator 30 of the present disclosure, a spirally-arrangedprotruding portion 32 that protrudes toward the exterior is provided onthe outer peripheral face 31B of shaft 31, and the spirally-arrangedprotruding portion 32 has gaps between sections that are neighboringalong the axis A of the shaft 31. This configuration not only enablesthe dilator to be moved forward in a conventional fashion by a pressingoperation, but also to be moved forward by a rotation operation as aresult of the spirally-arranged protruding portion 32.

Furthermore, the pitch of sections provided on the tapered part 34, saidsections being neighboring along the axis A of the spirally-arrangedprotruding portion 32, is configured to be larger than the pitch ofsections provided on the proximal end part 33, said sections beingneighboring along the axis A of the spirally-arranged protruding portion32. As a result, when the dilator 30 is rotated, the tapered part 34 ofthe shaft 31 has a smaller frictional resistance with the target object(for example, a digestive tract such as the stomach, or the liver) thanthe proximal end part 33. As a result, the diameter of apenetration-hole formed in the wall of a digestive tract or the like canbe easily widened, and it is possible to suppress damage to the targetobject which can occur due to intrusion into the target object.

Although the embodiments of the present disclosure have been describedabove, the present disclosure is not limited to these embodiments, andvarious modifications can be made.

For example, as shown in FIG. 5, the dilator 1 may be a dilator 100 inwhich the second coil 5 has gaps between sections that are neighboringalong the axial direction of the first coil 3 up to the proximal endthereof.

Furthermore, in terms of the spirally-arranged protruding portion 22 ofthe dilator 20 shown in FIG. 3, the pitch of sections provided on thetapered part 24, said sections being neighboring along the axis A of thespirally-arranged protruding portion 22, is configured to be larger thanthe pitch of sections provided on the proximal end part 23 and thedistal end part 25, said sections being neighboring along the axis A ofthe spirally-arranged protruding portion 22. However, like the dilator40 shown in FIG. 6, the pitches (L21 and L22) of sections provided onthe tapered part 24 and the proximal end part 23, said sections beingneighboring along the axis A of the spirally-arranged protruding portion22, may be configured to be larger than the pitch (L23) of sectionsprovided on the distal end part 25, said sections being neighboringalong the axis A of the spirally-arranged protruding portion 22. That isto say, a configuration is possible where L23<L21, L22 (all the pitchesL23 are smaller than any of the pitches L21 and any of the pitches L22).Note that the pitches on the distal end part 25 may be equal ordifferent. The pitches on the tapered part 24 and the proximal end part23 may be equal or different. As a result, when the dilator 40 isrotated, the tapered part 24 of the shaft 21 has a smaller frictionalresistance with the target object (for example, a digestive tract suchas the stomach, or the liver) than the distal end part 25. As a result,the diameter of a penetration-hole formed in the wall of a digestivetract or the like can be easily widened, and it is possible to suppressdamage to the target object which can occur due to intrusion into thetarget object.

Furthermore, like the dilator 50 shown in FIG. 7, the pitches (L22 andL23) of sections provided on the tapered part 24 and the distal end part25, said sections being neighboring along the axis A of thespirally-arranged protruding portion 22, may be configured to be largerthan the pitch (L21) of sections provided on the proximal end part 23,said sections being neighboring along the axis A of thespirally-arranged protruding portion 22. That is to say, a configurationis possible where L21<L23, L22 (all the pitches L21 are smaller than anyof the pitches L22 and and any of the pitches L23). Note that thepitches on the proximal end part 23 may be equal or different. Thepitches on the tapered part 24 and the distal end part 25 may be equalor different. As a result, when the dilator 50 is rotated, the taperedpart 24 of the shaft 21 has a smaller frictional resistance with thetarget object (for example, a digestive tract such as the stomach, orthe liver) than the proximal end part 23. As a result, the diameter of apenetration-hole formed in the wall of a digestive tract or the like canbe easily widened, and it is possible to suppress damage to the targetobject which can occur due to intrusion into the target object.

Furthermore, in the embodiments described above, a dilator 1 wasdescribed in which the shaft and the spirally-arranged protrudingportion are both constituted by a coil, and dilators 20, 30, 40, and 50were described in which the shafts 21 and 31, and the spirally-arrangedprotruding portions 22 and 32 are integrally formed by casting or thelike. However, the dilator may be formed such that only the shaft isformed by casting, and the spirally-arranged protruding portion isconstituted by a coil. That is to say, the dilator also may be a dilator200 configured by a shaft 21 and a spirally-arranged protruding portion(second coil 5) as shown in FIG. 8, a dilator 300 configured by a shaft31 and a spirally-arranged protruding portion (second coil 5) as shownin FIG. 9, a dilator 400 configured by a shaft 21 and aspirally-arranged protruding portion (second coil 5) as shown in FIG.10, or a dilator 500 configured by a shaft 21 and a spirally-arrangedprotruding portion (second coil 5) as shown in FIG. 11.

Note that the pitches of sections, being neighboring along the axis A ofthe spirally-arranged protruding portion, (second coil 5) are configuredin the dilator 200 of FIG. 8 such that L21, L23<L22, are configured inthe dilator 300 of FIG. 9 such that L31<L32, are configured in thedilator 400 of FIG. 10 such that L23<L21, L22, and are configured in thedilator 500 of FIG. 11 such that L21<L22, L23.

Furthermore, as shown in FIG. 12, in the dilator 1 (FIG. 1), the dilator20 (FIG. 3), and the dilator 200 (FIG. 8), the pitch of sectionsprovided on the tapered parts 3D and 24, said sections being neighboringalong the axis A of the second coil 5 and the spirally-arrangedprotruding portion 22, is configured to be larger than the pitch ofsections provided on the proximal end parts 3C and 23 and the distal endparts 3E and 25, said sections being neighboring along the axis A of thesecond coil 5 and the spirally-arranged protruding portion 22. That isto say, as shown in FIG. 12, in terms of the sections neighboring alongthe axis A of the second coil 5 and the spirally-arranged protrudingportion 22, the pitch La on the distal end parts 3E and 25, the pitch Lbon the tapered parts 3D and 24, and the pitch Lc on the distal end sideof the proximal end parts 3C and 23 are configured such that La, Lc<Lb.

However, if the relationship La<Lb is satisfied, for example, dilators1A, 20A, and 200A, where La<Lb=Lc (see FIG. 13), and the dilators 1B,20B, and 200B, where La<Lb<Lc (see FIG. 14) are also possible.Furthermore, if the relationship Lc<Lb is satisfied, for example,dilators 1C, 20C, and 200C, where Lc<Lb=La (see FIG. 15), and dilators1D, 20D, and 200D, where Lc<Lb<La (see FIG. 16) are also possible.

Note that the dilators 1A, 1B, 1C, and 1D are the embodiments ofdilators where the shaft and the spirally-arranged protruding portionare both configured by a coil like the dilator of FIG. 1, the dilators20A, 20B, 20C, and 20D are the embodiments of dilators where the shaftand the spirally-arranged protruding portion are both integrally formedby casting or the like as in the dilator of FIG. 3, and further, thedilators 200A, 200B, 200C, and 200D are the embodiments of dilatorswhere the shaft is formed by casting or the like, and thespirally-arranged protruding portion is configured by a coil like thedilator of FIG. 8.

Furthermore, in a dilator where the shaft and the spirally-arrangedprotruding portion are both integrally formed by casting or the like ina similar fashion to the dilator of FIG. 3, the spirally-arrangedprotruding portion may be provided up to the proximal end of the shaft.Moreover, in all of the dilators shown in the other diagrams, the secondcoil provided on the outer circumference of the shaft may or may nothave gaps between sections that are neighboring along the axis of theshaft up to the proximal end thereof.

Moreover, in the embodiments above, although the first coil 3 wasdescribed as a hollow coil body formed from ten wires, the number ofwires is not limited to ten, and may be one or more. In addition, in theembodiments above, although the second coil 5 was described as a hollowcoil body formed from a single wire, the number of wires is not limitedto one, and may be one or more.

Furthermore, although the tip 6 of the dilator 10 is formed by pouring abrazing material into the distal end of the multilayered body 17, a tip6 having a flat surface may be formed by polishing the outercircumference of the second coil 5 and/or the first coil 3 near thedistal end part of the multilayered body 17.

Moreover, although the tip 6 of the dilator 10 shown in FIG. 2 is fixedto the distal end of the multilayered body 17, the tip 6 may be fixed tothe distal end of any of the dilators shown in the other drawings, suchas the distal end of the shaft 21 of the dilator 20, or the distal endof the shaft 31 of the dilator 30.

Furthermore, the multilayered bodies 7 and 17 of the dilators 1, 10, and100, and the outer circumference of the spirally-arranged protrudingportions 22 and 32 of the dilators 20, 30, 40, 50, 200, 300, 400, and500 may be coated with a resin. For example, as shown in FIG. 17, theouter circumference of the shaft 21 and the spirally-arranged protrudingportion 22 of the dilator 20 may be coated with a resin 26. The resin 26can improve the slidability. Also, as a result of this coating, in theembodiments where the shaft is constituted by the first coil, it ispossible to inhibit living tissue from becoming trapped between thewires of the first coil (sections that are neighboring along the shaftaxis of the first coil constituting the shaft), or in the embodimentswhere the spirally-arranged protruding portion includes the second coil,it is possible to inhibit living tissue from becoming trapped betweenthe second coil and the shaft. When the outer circumference of the shaft21 is coated by the resin 26, the sections of the proximal end part 23,the tapered part 24, and the distal end part 25 that are coated by theresin 26 correspond to the shaft 21, and the sections that protrudetoward the exterior from the outer peripheral face 21B of the shaft 21correspond to the spirally-arranged protruding portion 22. Examples ofthe resin 26 include biocompatible resin materials such as polyamideresins and fluororesins, and hydrophilic coating materials, and thethickness thereof is, for example, 0.1 to 300 μm. In addition, althoughthe shafts 21 and 31 were integrally formed with the spirally-arrangedprotruding portions 22 and 32, these may be separately formed.

In the embodiments shown in FIG. 1 to FIG. 17, dilators not having acoating on the surface of the shaft (other than the resin 36 in FIG. 17)were described. However, the shaft may have various coatings on thesurface side (including parts between the shaft and thespirally-arranged protruding portion). Examples of the coating include aprotective film (a typical example being a plating film) on the surfaceof the shaft, and a base film for improving the adhesion between theshaft and the spirally-arranged protruding portion.

In the embodiments shown in FIG. 1 to FIG. 17, the spirally-arrangedprotruding portion preferably does not constitute a blade. The dilatorsof the present embodiments expand a pre-formed penetration-hole in atarget object (an example being the wall of a digestive tract such as apatient's stomach). Therefore, if the spirally-arranged protrudingportion constitutes a blade, the living tissue on the inner surface ofthe penetration-hole becomes damaged.

Therefore, the cross-sectional shape of the spirally-arranged protrudingportion (for example, the shape of a cross-section taken orthogonally tothe helix direction of the spirally-arranged protruding portion shown inFIG. 3) preferably does not include a corner portion having an acuteangle on the radially outer end part of the shaft. That is to say, theend part preferably has a part which is formed having, for example, ashape which contains a corner portion having an obtuse angle, or a curve(for example, a curve containing part of a circle or an ellipse).

1. A dilator comprising: a shaft having a hollow shape, the shaftcomprising: a tapered portion having an outer diameter that is smallerat a distal end of the tapered portion than at a proximal end of thetapered portion; a proximal end portion that is provided on a proximalside of the tapered portion and that extends in a proximal direction;and optionally, a distal end portion that is provided on a distal sideof the tapered portion and that extends in a distal direction; and aspirally-arranged protruding portion provided on an outer peripheralsurface of the shaft, the spirally-arranged protruding portion havinggaps between adjacent sections of the spirally-arranged protrudingportion along a longitudinal axis of the shaft, wherein: in a case wherethe shaft does not include the distal end portion, a pitch of theadjacent sections of the spirally-arranged protruding portion providedon the tapered portion is larger than a pitch of the adjacent sectionsof the spirally-arranged protruding portion provided on the proximal endportion, and in a case where the shaft includes the distal end portion,the pitch of the adjacent sections of the spirally-arranged protrudingportion provided on the tapered portion is larger than (i) a pitch ofthe adjacent sections of the spirally-arranged protruding portionprovided on the distal end portion or (ii) the pitch of the adjacentsections of the spirally-arranged protruding portion provided on theproximal end portion.
 2. The dilator according to claim 1, wherein inthe case where the shaft includes the distal end portion, the pitch ofthe adjacent sections of the spirally-arranged protruding portionprovided on the tapered portion is larger than both (i) the pitch of theadjacent sections of the spirally-arranged protruding portion providedon the distal end portion and (ii) the pitch of the adjacent sections ofthe spirally-arranged protruding portion provided on the proximal endportion.
 3. The dilator according to claim 1, wherein the shaft includesa coil comprising a wire wound into a hollow shape.
 4. The dilatoraccording to claim 1, wherein the spirally-arranged protruding portionincludes a coil comprising a wire wound around on the outer peripheralsurface of the shaft.
 5. The dilator according to claim 1, wherein: theshaft includes a first coil comprising a wire wound into a hollow shape,the spirally-arranged protruding portion includes a second coilcomprising a wire wound around on the outer peripheral surface of theshaft, and the wire of the first coil and the wire of the second coilare wound in opposite directions.
 6. The dilator according to claim 1,further comprising: a grip portion provided at a proximal end of theshaft.